The present disclosure relates generally to LED drive circuits and, more particularly, to LED drive circuits used for pulse oximetry.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors may desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices may have been developed for monitoring physiological characteristics of a patient. Such devices provide doctors and other healthcare personnel with the information they need to provide better healthcare for their patients.
One technique for monitoring certain physiological characteristics of a patient is commonly referred to as pulse oximetry, and the devices built based upon pulse oximetry techniques are commonly referred to as pulse oximeters. Pulse oximetry may be used to measure various blood flow characteristics, such as the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. In fact, the “pulse” in pulse oximetry refers to the time varying amount of arterial blood in the tissue during each cardiac cycle.
Pulse oximeters typically utilize a non-invasive sensor that transmits light through a patient's tissue and that photoelectrically senses the absorption and/or scattering of the transmitted light in such tissue. One or more of the above physiological characteristics may then be calculated based upon the amount of light absorbed or scattered. More specifically, the light passed through the tissue is typically selected to be of one or more wavelengths that may be absorbed and/or scattered by the blood in an amount correlative to the amount of the blood constituent present in the blood. The amount of light absorbed and/or scattered may then be used to estimate the amount of blood constituent in the tissue using various algorithms. Changes in the amount of arterial blood in the tissue during a blood pressure pulse may change the amount and character of the light detected by the sensor's photodetector.
More specifically, within the field of pulse oximetry, the blood oxygen level of a patient may be determined by measuring the differential absorption of light produced by red and infrared emitters. Typically, the emitters are two types of LEDs that are turned on in sequence by an LED drive circuit which controls the activation of each LED at the proper time. However, LED drive circuits may use a large number of component parts. Each part may introduce a potential point of failure in manufacture and during the operation of the pulse oximeter. Furthermore, because of the large number of parts, LED drive circuits tend to be fairly large in size to accommodate the number of parts.